Composition for dyeing keratin fibres, comprising a cationic diazo direct dye containing a 2-imidazolium unit

ABSTRACT

The present invention relates to a composition for dyeing keratin fibres, comprising at least one cationic diazo direct dye chosen from the compounds of formula (I) or (II) below, the mesomeric forms thereof, and also the acid-addition salts thereof and solvates thereof. The invention allows the production of colorations that are resistant to the various attacking factors to which the hair may be subjected, especially to shampooing. The invention also makes it possible to obtain blue or violet colorations, especially sparingly chromatic blue colorations, which lead to fundamental and/or natural shades. Moreover, the direct dyes used in the context of the invention are light-stable and stable under standard lightening dyeing conditions, in particular in the presence of an oxidizing agent and/or of ammonia.

The present invention relates to a composition for dyeing keratin fibres, and in particular human keratin fibres such as the hair, comprising at least one cationic diazo direct dye containing a 2-imidazolium unit.

It is known practice to dye keratin fibres, and in particular human keratin fibres such as the hair, with dye compositions containing direct dyes. These compounds are coloured and colouring molecules with affinity for the fibres. It is known practice, for example, to use direct dyes of nitrobenzene type, anthraquinone or nitropyridine dyes and dyes of the azo, xanthene, acridine, azine or triarylmethane type.

Usually, these dyes are applied to the fibres, optionally in the presence of an oxidizing agent, if it is desired to obtain simultaneous lightening of the fibres. Once the leave-on time has elapsed, the fibres are rinsed, optionally washed, and dried.

The colorations resulting from the use of direct dyes are temporary or semi-permanent colorations since the nature of the interactions that bind the direct dyes to the keratin fibre, and their desorption from the surface and/or core of the fibre, are responsible for their low dyeing power and their poor relative fastness to washing or perspiration.

Certain direct dyes may be unstable under standard lightening dyeing conditions and/or they have insufficient photostability properties.

There are in particular few blue or violet direct dyes that do not have these drawbacks. However, these dyes have the advantage of allowing fundamental and/or natural shades to be obtained.

The aim of the present invention is to provide direct dyes that do not have the drawbacks of the existing direct dyes.

In particular, one of the aims of the present invention is to provide blue or violet direct dyes, which are stable in oxidizing medium or light-stable, which make it possible to obtain colorations that are resistant over time with respect to external attacking factors such as light, bad weather, washing, perspiration and rubbing.

This aim is achieved with the present invention, one subject of which is a composition for dyeing keratin fibres, comprising, in a suitable dyeing medium, at least one cationic diazo direct dye containing a 2-imidazolium unit, chosen from the compounds of formula (I) or (II) below, the mesomeric forms thereof, and also the acid-addition salts thereof, and the solvates thereof:

in which:

-   -   the radicals R₁ represent, independently of each other:         -   a linear or branched, saturated, acyclic, optionally             substituted C₁-C₈ hydrocarbon-based chain, optionally             interrupted with one or more heteroatoms and/or with one or             more groups comprising at least one heteroatom, preferably             chosen from oxygen, nitrogen or sulfur, CO, SO and SO₂, or             combinations thereof; the hydrocarbon-based chain not             comprising any nitro, nitroso, peroxo or diazo functions and             being necessarily attached to the quaternized or             non-quaternized nitrogen atom of the imidazolium ring via a             carbon atom;         -   an optionally substituted phenyl radical;         -   an optionally substituted benzyl radical;     -   the radicals R₂ represent, independently of each other:         -   a linear C₁-C₄ alkyl radical, optionally substituted with an             amino radical or a hydroxyl radical;         -   an optionally substituted phenyl radical;         -   a halogen atom;     -   the radicals R₃ represent, independently of each other:         -   a linear C₁-C₄ alkyl radical, optionally substituted with an             amino radical or a hydroxyl radical;         -   a hydroxyl radical;         -   a C₁-C₄ alkoxy radical;         -   a C₁-C₄ monohydroxyalkoxy or polyhydroxyalkoxy radical;         -   an amino radical optionally substituted with one or two             C₁-C₄ alkyl radicals, which may be identical or different,             optionally bearing at least one hydroxyl radical;         -   a group R_(a)CO—NR_(a)— in which the radical R_(a)             represents a C₁-C₄ alkyl radical; the radical R_(a)′             represents a hydrogen atom or a C₁-C₄ alkyl radical;         -   a group (R_(b))₂N—CO— in which the radicals R_(b) represent,             independently of each other, a hydrogen atom or a C₁-C₄             alkyl radical;         -   a group (R_(c))₂N—CO—NR_(c)— in which the radicals R_(c)             represent, independently of each other, a hydrogen atom or a             C₁-C₄ alkyl radical;         -   a group (R_(d))₂N—SO₂— in which the radicals R_(d)             represent, independently of each other, a hydrogen atom or a             C₁-C₄ alkyl radical;         -   a group R_(e)SO₂—NR_(c)— in which the radicals R_(e)             represent, independently of each other, a hydrogen atom or a             C₁-C₄ alkyl radical;         -   a cyano radical;         -   a halogen atom, preferably chlorine or fluorine;     -   the radicals R₄ represent, independently of each other:         -   a linear C₁-C₄ alkyl radical;         -   a hydroxyl radical;         -   a C₁-C₄ alkoxy radical;         -   a C₁-C₄ monohydroxyalkoxy or polyhydroxyalkoxy radical;         -   an amino radical optionally substituted with one or two             C₁-C₄ alkyl radicals, which may be identical or different,             optionally bearing at least one hydroxyl radical; the two             alkyl radicals possibly forming, together with the nitrogen             atom to which they are attached, a 5- or 6-membered             heterocycle optionally comprising another heteroatom             identical to or different from nitrogen, such as a             pyrrolidine, morpholine or piperidine ring, optionally             substituted with one or more methyl, hydroxyl, amino,             monomethylamino or dimethylamino radicals;         -   a group R_(a)CO—NR_(a)′— in which the radical R_(a)             represents a C₁-C₄ alkyl radical; the radical R_(a)′             represents a hydrogen atom or a C₁-C₄ alkyl radical;         -   a group (R_(b))₂N—CO— in which the radicals R_(b) represent,             independently of each other, a hydrogen atom or a C₁-C₄             alkyl radical;         -   a group (R_(c))₂N—CO—NR_(c)— in which the radicals R_(c)             represent, independently of each other, a hydrogen atom or a             C₁-C₄ alkyl radical;         -   a group (R_(d))₂N—SO₂— in which the radicals R_(d)             represent, independently of each other, a hydrogen atom or a             C₁-C₄ alkyl radical;         -   a group R_(e)SO₂—NR_(e)— in which the radicals R_(e)             represent, independently of each other, a hydrogen atom or a             C₁-C₄ alkyl radical;         -   a cyano radical;         -   a halogen atom, preferably chlorine or fluorine;     -   the radicals R₅ and R₆, which may be identical or different,         represent:         -   a hydrogen atom;         -   a linear or branched, saturated, acyclic, optionally             substituted C₁-C₈ hydrocarbon-based chain, optionally             interrupted with one or more heteroatoms and/or with one or             more groups comprising at least one heteroatom, preferably             chosen from oxygen, nitrogen, sulfur, CO, SO and SO₂, or             combinations thereof; the hydrocarbon-based chain not             comprising any nitro, nitroso, peroxo or diazo functions and             being necessarily attached to the nitrogen atom via a carbon             atom;         -   a radical (R_(f)SO₂—) in which the radical R_(f) represents             a C₁-C₄ alkyl radical;         -   a benzyl radical optionally substituted with         -   one or more hydroxyl and/or amino radicals; the radicals R₅             and R₆ possibly forming, with the nitrogen atom to which             they are attached, a saturated or unsaturated, optionally             substituted 5- or 7-membered heterocycle, optionally             comprising another heteroatom that is identical to or             different from nitrogen;         -   one of the radicals R₅ and R₆ possibly forming, with the             nitrogen atom to which it is attached and with a radical R₄             located ortho to the group NR₅R₆, an optionally substituted             5- or 6-membered heterocycle of formula (III) below:

-   -   in which:         -   o is an integer equal to 0 or 1;         -   Rx and Ry represent, independently of each other, a hydrogen             atom or a methyl radical;         -   the radicals R₅ and R₆ possibly forming, with the nitrogen             atom to which they are attached and each with a radical R₄             located ortho to the group NR₅R₆, an optionally substituted             5- or 6-membered heterocycle of formula (IV) below:

-   -   in which:         -   o is an integer equal to 0 or 1;         -   Rx and Ry represent, independently of each other, a hydrogen             atom or a methyl radical;         -   n is an integer between 0 and 2; when n is less than 2, the             unsubstituted carbon atom(s) bear(s) a hydrogen atom;         -   n′ is an integer between 0 and 4 and preferably between 0             and 2; when n′ is less than 4, the unsubstituted carbon             atom(s) bear(s) a hydrogen atom;         -   n″ is an integer between 0 and 4 and preferably between 0             and 3; when n″ is less than 4, the unsubstituted carbon             atom(s) bear(s) a hydrogen atom;             the electrical neutrality of the compounds of formula (I)             or (II) being assured by one or more identical or different             cosmetically acceptable anions An.

A subject of the present invention is also a process for dyeing keratin fibres using the composition in accordance with the present invention.

A subject of the present invention is also a multi-compartment device for performing the process in accordance with the invention.

A subject of the present invention is also the use for dyeing keratin fibres of the composition in accordance with the invention.

A subject of the present invention is also novel cationic diazo direct dyes.

The present invention allows the production of colorations that are resistant to the various attacking factors to which the hair may be subjected, and especially to shampooing.

The present invention also allows blue or violet colorations to be obtained, especially sparingly chromatic blue colorations, which lead to fundamental and/or natural shades.

Moreover, the direct dyes used in the context of the invention are light-stable and stable under standard lightening dyeing conditions, in particular in the presence of an oxidizing agent and/or of ammonia.

Unless otherwise indicated, the limits of the ranges of values that are given below are included in these ranges.

For the purposes of the present invention, and unless otherwise indicated:

-   -   an alkyl radical or the alkyl part of a radical is linear or         branched;     -   an alkyl radical or the alkyl part of the radical is said to be         substituted when it comprises at least one substituent chosen         from the following groups:         -   hydroxyl;         -   C₁-C₄ alkoxy or C₁-C₄ monohydroxyalkoxy or             poly-hydroxyalkoxy;         -   amino optionally substituted with one or two C₁-C₄ alkyl             radicals, which may be identical or different, optionally             bearing at least one hydroxyl radical, the said alkyl             radicals possibly forming with the nitrogen atom to which             they are attached a 5- or 6-membered heterocycle optionally             comprising at least one other heteroatom that may or may not             be different from nitrogen;     -   a hydrocarbon-based chain is said to be substituted when it         comprises at least one substituent chosen from the following         groups:         -   hydroxyl;         -   C₁-C₄ alkoxy or C₁-C₄ monohydroxyalkoxy or             poly-hydroxyalkoxy;         -   amino optionally substituted with one or two C₁-C₄ alkyl             radicals, which may be identical or different, optionally             bearing at least one hydroxyl radical, said alkyl radicals             possibly forming, with the nitrogen atom to which they are             attached, a 5- or 6-membered heterocycle optionally             comprising at least one other heteroatom that may or may not             be different from nitrogen;     -   an aryl or heteroaryl radical or the aryl or heteroaryl part of         a radical is said to be substituted when it comprises at least         one substituent borne by a carbon atom chosen from:         -   a C₁-C₁₆ and preferably C₁-C₈ alkyl radical optionally             substituted with one or more radicals chosen from the             following radicals: hydroxyl, C₁-C₂ alkoxy, C₁-C₄             monohydroxyalkoxy or polyhydroxyalkoxy, C₁-C₄             alkylcarbonylamino, amino substituted with two C₁-C₄ alkyl             radicals, which may be identical or different, optionally             bearing at least one hydroxyl radical, the two radicals             possibly forming, with the nitrogen atom to which they are             attached, a 5- to 7-membered and preferably 5- or 6-membered             heterocycle, optionally comprising another heteroatom that             is identical to or different from nitrogen;         -   a halogen atom such as chlorine, fluorine or bromine;         -   a hydroxyl radical;         -   a C₁-C₂ alkoxy radical;         -   a C₁-C₄ monohydroxyalkoxy or polyhydroxyalkoxy radical;         -   an amino radical optionally substituted with one or two             C₁-C₄ alkyl radicals, which may be identical or different,             optionally bearing at least one hydroxyl or amino radical             substituted with two optionally substituted C₁-C₂ alkyl             radicals;         -   a radical —NR_(a)′—COR_(a) in which the radical R_(a)             represents a C₁-C₄ alkyl radical; the radical R_(a)′             represents a hydrogen atom or a C₁-C₄ alkyl radical;         -   a radical (R_(b))₂N—CO— in which the radicals R_(b), which             may be identical or different, represent a C₁-C₄ alkyl             radical;         -   a radical R_(e)SO₂—NR_(e)— in which the radicals R_(e)             represent, independently of each other, a hydrogen atom, a             C₁-C₄ alkyl radical or a phenyl radical;         -   a radical (R_(d))₂N—SO₂— in which the radicals R_(d), which             may be identical or different, represent a hydrogen atom or             a C₁-C₄ alkyl radical;     -   the cyclic or heterocyclic part of a non-aromatic radical is         said to be substituted when it comprises at least one         substituent borne by a carbon atom chosen from the following         groups:         -   hydroxyl;         -   C₁-C₄ alkoxy; C₁-C₄ monohydroxyalkoxy or poly-hydroxyalkoxy.

According to one particular embodiment of the invention, the radicals R₁ are chosen from a C₁-C₄ alkyl radical, optionally ending with a hydroxyl. By way of example, the radicals R₁ represent a methyl radical, an ethyl radical or a 2-hydroxyethyl radical.

According to another particular embodiment of the invention, n is equal to 0 or the radicals R₂ are chosen from a C₁-C₄ alkyl radical optionally substituted with an amino radical or a hydroxyl radical. By way of example, the radicals R₂ are chosen from a methyl radical; an ethyl radical; a 2-hydroxyethyl radical; a 3-aminopropyl radical.

According to another particular embodiment of the invention, the radicals R₃ are chosen from a C₁-C₄ alkyl radical; a C₁-C₄ alkoxy radical; a halogen atom; an optionally substituted amino radical; a group R_(a)CO—NR_(a)′— in which the radical R_(a) represents a C₁-C₄ alkyl radical; the radical R_(a)′ represents a hydrogen atom; a hydroxyl radical. By way of example, the radicals R₃ are chosen from a methyl radical; a methoxy radical; a chlorine atom; a hydroxyl radical; a methylcarbonyl-amino radical.

According to another particular embodiment of the invention, the radicals R₄ are chosen from an alkyl radical; a hydroxyl radical; an alkoxy radical; a C₁-C₄ mono(alkyl)amino or di(alkyl)amino radical; a C₁-C₄ di(hydroxyalkyl)amino radical; a halogen atom; a group R_(a)CO—NR_(a)′— in which the radical R_(a) represents a C₁-C₄ alkyl radical and the radical R_(a)′ represents a hydrogen atom. By way of example, the radicals R₄ are chosen from a methyl radical; a hydroxyl radical; an ethyl-amino radical; a dimethylamino radical; a bis(2-hydroxyethyl)amino radical; a chlorine atom; a methyl-carbonylamino radical.

According to another particular embodiment of the invention, the radicals R₅ and R₆, which may be identical or different, represent:

-   -   a C₁-C₄ alkyl radical, optionally substituted with at least one         hydroxyl radical;     -   a benzyl radical optionally substituted with one or more         hydroxyl and/or amino radicals.

According to another particular embodiment of the invention, the radicals R₅ and R₆ form, together with the nitrogen atom to which they are attached, a saturated or unsaturated, optionally substituted 5- or 7-membered heterocycle, optionally comprising another heteroatom, which may be identical to or different from nitrogen, for instance a pyrrolidine, piperazine, homo-piperazine or piperidine nucleus.

According to another particular embodiment of the invention, one of the radicals R₅ or R₆ forms, with the nitrogen atom to which it is attached and with a radical R₄ located ortho to the group NR₅R₆, an optionally substituted 5- or 6-membered heterocycle of formula (III) below:

-   -   in which:         -   o is an integer equal to 0 or 1;         -   Rx and Ry represent, independently of each other, a hydrogen             atom or a methyl radical.

As examples of rings of formula (III), mention may be made of the following rings:

-   -   with p=0 or 1.

According to another particular embodiment of the invention, the radicals R₅ and R₆ form, with the nitrogen atom to which they are attached and each with a radical R₄ located ortho to the group NR₅R₆, an optionally substituted 5- or 6-membered heterocycle of formula (IV) below:

in which:

-   -   o is an integer equal to 0 or 1;     -   Rx and Ry, independently of each other, represent a hydrogen         atom or a methyl radical.

As examples of rings of formula (IV), mention may be made of the following rings:

-   -   with p=0 or 1.

In the compounds of formula (I) or (II), An represents an organic or mineral anion or mixture of anions, which makes it possible to balance the charge(s) on the compounds of formula (I) or (II), chosen, for example, from a halide such as a chloride, bromide, fluoride or iodide ion; a hydroxide; a sulfate; a hydrogen sulfate; an alkyl sulfate for which the linear or branched alkyl part is of C₁-C₆, for instance the methyl sulfate or ethyl sulfate ion; carbonates and hydrogen carbonates; carboxylic acid salts such as formate, acetate, citrate, tartrate or oxalate; alkylsulfonates for which the linear or branched alkyl part is of C₁-C₆, for instance the methylsulfonate ion; arylsulfonates for which the aryl part, preferably phenyl, is optionally substituted with one or more C₁-C₄ alkyl radicals, for instance 4-tolylsulfonate; alkylsulfonyls such as mesylate.

The acid-addition salts of the compounds of formula (I) or (II) may be, for example, the addition salts with an organic or mineral acid such as hydrochloric acid, hydrobromic acid, sulfuric acid or (alkyl- or phenyl-)sulfonic acids such as p-toluenesulfonic acid or methylsulfonic acid.

The solvates of the compounds of formula (I) or (II) represent the hydrates of such compounds and/or the combination of a compound of formula (I) or (II) with a linear or branched C₁-C₄ alcohol such as methanol, ethanol, isopropanol or n-propanol.

In the context of the present invention, the direct dyes of formula (I) or (II) are preferably chosen from the direct dyes of formula (I′) or (II′) below:

in which:

-   -   the radicals R′₁ represent, independently of each other, a C₁-C₄         alkyl radical; a 2-hydroxyethyl radical;     -   the radicals R′₃ represent, independently of each other, a C₁-C₄         alkyl radical; a C₁-C₄ alkoxy radical; a halogen atom; a         hydroxyl radical; a methylcarbonylamino radical;     -   m′ represents an integer equal to 0, 1 or 2;     -   the radicals R′₄ represent, independently of each other, a C₁-C₄         alkyl radical; a hydroxyl radical; an alkoxy radical; a         mono(alkyl)amino or di(alkyl)amino radical; a         di(hydroxyalkyl)amino radical; a halogen atom such as chlorine;         a (C₁-C₄)alkylcarbonylamino radical;     -   m″ represents an integer equal to 0, 1, 2 or 3;     -   the radicals R′₅ and R′₆ represent, independently of each other,         a C₁-C₄ alkyl radical; a C₁-C₄ mono-hydroxyalkyl radical; or         form, with one or two radicals R′₄ located ortho to the group         NR′₅R′₆ and the benzene nucleus to which they are attached, a         ring of formula (III) or (IV).

As examples of direct dyes of formula (I) or (II), mention may be made of the compounds presented in the table below, An being as defined previously:

Dye 1

Dye 2

Dye 3

Dye 4

Dye 5

Dye 6

Dye 7

Dye 8

Dye 9

Dye 10

Dye 11

The direct dyes of formula (I) or (II) that are useful in the context of the invention may be prepared, for example, according to the synthetic mode as described in patent U.S. Pat. No. 3,173,907 and detailed below.

They may in particular be synthesized according to the following procedure:

The direct dyes of formula (I) or (II) that are useful in the context of the invention may also be prepared according to the synthetic modes as described below.

The diazotization reaction of an aromatic amine (or of a 2-aminoimidazole or derivatives thereof) takes place in the presence of a diazotization reagent such as sodium nitrite in acidic medium (a mineral acid such as hydrochloric acid or orthophosphoric acid or an organic acid such as acetic acid). The amine function is then converted into a diazonium salt. Other reagents may be more suitable if the diazonium salt under consideration is unstable in aqueous medium; examples that will be mentioned include alkyl nitrites, such as amyl nitrite, or nitrosylsulfuric acid. These reagents are formal equivalents of nitrous acid. The diazonium salt may be used in the following step directly (use of the reaction mixture), after having been isolated (for example by precipitation and vacuum filtration) or after modification of the characteristics of the mixture (modification of pH, dilution, concentration, addition of a solvent other than the initial solvent).

Where appropriate, the excess diazotization reagents used during the first step may be destroyed at the end of the operation by adding sulfamic acid or urea to the reaction medium.

The step that consists in reacting the diazonium salt obtained beforehand with an aromatic amine (or an imidazole or derivatives thereof) is possible either by pouring a solution of the latter reagent into the solution of diazonium salt as obtained after the first step (or by redissolving the isolated diazonium salt), or, conversely, by pouring the solution of diazonium salt into the solution of the aromatic amine (or of the imidazole or derivatives thereof). The pH of the reaction medium is adjusted by adding a base since the “coupling” reaction normally takes place at a pH higher than that of the diazotization step. The base may be introduced into the reaction medium before, but preferably at the same time or after, the placing in contact of the aromatic amine and the diazonium salt. This sequence of two reactions leads to the formation of an azo compound.

The diazotization reaction is preferably performed in an acidified polar (a) protic solvent, such as water acidified with hydrochloric acid, acetic acid or sulfuric acid, where appropriate in the presence of a cosolvent such as ethyl alcohol, THF or dioxane, at a pH below 6. The temperature is less than 40° C. and preferably less than 15° C. The reaction time is between one minute and twentyfour hours.

The coupling of the diazonium salt thus formed and of the aromatic amine may take place in the same solvent, to which a cosolvent may be added, the pH possibly being raised by adding an organic or mineral base such as sodium hydroxide to the reaction medium. The temperature is maintained below 40° C. and preferably below 15° C. The reaction takes place in a time of between one minute and twentyfour hours.

The alkylation step is performed with an alkylating reagent such as an alkyl sulfate, an alkyl halide, an alkyl alkylsulfonate or an alkyl arylsulfonate. It is also possible to use an oxirane to perform this alkylation.

The alkylation reaction takes place, for example, in a halogenated solvent, for example dichloromethane or 1,2-dichloroethane, or an ester, for example ethyl acetate, at a temperature below 150° C., preferably at the reflux point of the solvent, in the presence of a mineral base (MgO, K₂CO₃, Na₂CO₃, etc.) or an organic salt (Na⁺OAc⁻, etc.).

The cationic dyes precipitate in apolar solvents, which allows them to be isolated and purified.

The direct dye(s) used in the context of the invention generally represent(s) from 0.01% to 5% by weight relative to the total weight of the composition and more particularly from 0.05% to 2% by weight relative to the total weight of the composition.

The composition according to the invention may also comprise an oxidation base. This oxidation base may be chosen from the oxidation bases conventionally used in oxidation dyeing, for example para-phenylenediamines, bis(phenyl)alkylenediamines, para-aminophenols, ortho-aminophenols and heterocyclic bases.

Among the para-phenylenediamines that may be mentioned more particularly are, for example, para-phenylene-diamine, para-tolylenediamine, 2-chloro-para-phenylenediamine, 2,3-dimethyl-para-phenylenediamine, 2,6-dimethyl-para-phenylenediamine, 2,6-diethyl-para-phenylenediamine, 2,5-dimethyl-para-phenylenediamine, N,N-dimethyl-para-phenylenediamine, N,N-diethyl-para-phenylenediamine, N,N-dipropyl-para-phenylenediamine, 4-amino-N,N-diethyl-3-methylaniline, N,N-bis(β-hydroxy-ethyl)-para-phenylenediamine, 4-N,N-bis(β-hydroxy-ethyl)amino-2-methylaniline, 4-N,N-bis(β-hydroxyethyl)-amino-2-chloroaniline, 2-p-hydroxyethyl-para-phenylene-diamine, 2-fluoro-para-phenylenediamine, 2-isopropyl-para-phenylenediamine, N-(β-hydroxypropyl)-para-phenylenediamine, 2-hydroxymethyl-para-phenylene-diamine, N,N-dimethyl-3-methyl-para-phenylenediamine, N-ethyl-N-(β-hydroxyethyl)-para-phenylenediamine, N-(β,γ-dihydroxypropyl)-para-phenylenediamine, N-(4′-aminophenyl)-para-phenylenediamine, N-phenyl-para-phenylenediamine, 2-p-hydroxyethyloxy-para-phenylene-diamine, 2-β-acetylaminoethyloxy-para-phenylenediamine, N-(β-methoxyethyl)-para-phenylenediamine, 4-amino-phenylpyrrolidine, 2-thienyl-para-phenylenediamine, 2-β-hydroxyethylamino-5-aminotoluene, and the addition salts thereof with an acid.

Among the para-phenylenediamines mentioned above, para-phenylenediamine, para-tolylenediamine, 2-isopropyl-para-phenylenediamine, 2-β-hydroxyethyl-para-phenylene-diamine, 2-β-hydroxyethyloxy-para-phenylenediamine, 2,6-dimethyl-para-phenylenediamine, 2,6-diethyl-para-phenylenediamine, 2,3-dimethyl-para-phenylenediamine, N,N-bis(β-hydroxyethyl)-para-phenylenediamine, 2-chloro-para-phenylenediamine and 2-β-acetylamino-ethyloxy-para-phenylenediamine, and the addition salts thereof with an acid, are particularly preferred.

Among the bis(phenyl)alkylenediamines that may be mentioned, for example, are N,N′-bis(β-hydroxyethyl)-N,N′-bis(4′-aminophenyl)-1,3-diaminopropanol, N,N′-bis-(β-hydroxyethyl)-N,N′-bis(4′-aminophenyl)ethylene-diamine, N,N′-bis(4-aminophenyl)tetramethylenediamine, N,N′-bis(β-hydroxyethyl)-N,N′-bis(4-aminophenyl)tetra-methylenediamine, N,N′-bis(4-methylaminophenyl)tetra-methylenediamine, N,N′-bis(ethyl)-N,N′-bis(4′-amino-3′-methylphenyl)ethylenediamine and 1,8-bis(2,5-diamino-phenoxy)-3,6-dioxaoctane, and the addition salts thereof with an acid.

Among the para-aminophenols that may be mentioned, for example, are para-aminophenol, 4-amino-3-methylphenol, 4-amino-3-fluorophenol, 4-amino-3-hydroxymethylphenol, 4-amino-2-methylphenol, 4-amino-2-hydroxymethylphenol, 4-amino-2-methoxymethylphenol, 4-amino-2-aminomethyl-phenol, 4-amino-2-(β-hydroxyethylaminomethyl)phenol and 4-amino-2-fluorophenol, and the addition salts thereof with an acid.

Among the ortho-aminophenols that may be mentioned, for example, are 2-aminophenol, 2-amino-5-methylphenol, 2-amino-6-methylphenol and 5-acetamido-2-aminophenol, and the addition salts thereof with an acid.

Among the heterocyclic bases that may be mentioned, for example, are pyridine derivatives, pyrimidine derivatives and pyrazole derivatives, and derivatives of pyrazolo[1,2-a]pyrazol-1-one type.

Among the pyridine derivatives that may be mentioned are the compounds described, for example, in patents GB 1 026 978 and GB 1 153 196, such as 2,5-diamino-pyridine, 2-(4-methoxyphenyl)amino-3-aminopyridine, 2,3-diamino-6-methoxypyridine, 2-(β-methoxyethyl)amino-3-amino-6-methoxypyridine and 3,4-diaminopyridine, and the addition salts thereof with an acid.

Among the pyrimidine derivatives that may be mentioned are the compounds described, for example, in patents DE 2 359 399; JP 88-169 571; JP 05-163 124; EP 0 770 375 or patent application WO 96/15765, such as 2,4,5,6-tetraminopyrimidine, 4-hydroxy-2,5,6-triamino-pyrimidine, 2-hydroxy-4,5,6-triaminopyrimidine, 2,4-dihydroxy-5,6-diaminopyrimidine and 2,5,6-triamino-pyrimidine, and pyrazolopyrimidine derivatives such as those mentioned in patent application FR-A-2 750 048 and among which mention may be made of pyrazolo[1,5-a]pyrimidine-3,7-diamine; 2,5-dimethylpyrazolo[1,5-a]pyrimidine-3,7-diamine; pyrazolo[1,5-a]pyrimidine-3,5-diamine; 2,7-dimethylpyrazolo[1,5-a]pyrimidine-3,5-diamine; 3-aminopyrazolo[1,5-a]pyrimidin-7-ol; 3-amino-pyrazolo[1,5-a]pyrimidin-5-ol; 2-(3-aminopyrazolo[1,5-a]pyrimidin-7-ylamino)ethanol, 2-(7-aminopyrazolo[1,5-a]pyrimidin-3-ylamino)ethanol, 2-[(3-aminopyrazolo[1,5-a]pyrimidin-7-yl)(2-hydroxyethyl)amino]ethanol, 2-[(7-aminopyrazolo[1,5-a]pyrimidin-3-yl)(2-hydroxy-ethyl)amino]ethanol, 5,6-dimethylpyrazolo[1,5-a]-pyrimidine-3,7-diamine, 2,6-dimethylpyrazolo[1,5-a]-pyrimidine-3,7-diamine, 2,5,N7,N7-tetramethylpyrazolo-[1,5-a]pyrimidine-3,7-diamine and 3-amino-5-methyl-7-imidazolylpropylaminopyrazolo[1,5-a]pyrimidine, and the addition salts thereof with an acid and the tautomeric forms thereof, when a tautomeric equilibrium exists.

Among the pyrazole derivatives that may be mentioned are the compounds described in patents DE 3 843 892 and DE 4 133 957 and patent applications WO 94/08969, WO 94/08970, FR-A-2 733 749 and DE 195 43 988, such as 4,5-diamino-1-methylpyrazole, 4,5-diamino-1-(β-hydroxy-ethyl)pyrazole, 3,4-diaminopyrazole, 4,5-diamino-1-(4′-chlorobenzyl)pyrazole, 4,5-diamino-1,3-dimethyl-pyrazole, 4,5-diamino-3-methyl-1-phenylpyrazole, 4,5-diamino-1-methyl-3-phenylpyrazole, 4-amino-1,3-dimethyl-5-hydrazinopyrazole, 1-benzyl-4,5-diamino-3-methylpyrazole, 4,5-diamino-3-tert-butyl-1-methyl-pyrazole, 4,5-diamino-1-tert-butyl-3-methylpyrazole, 4,5-diamino-1-(β-hydroxyethyl)-3-methylpyrazole, 4,5-diamino-1-ethyl-3-methylpyrazole, 4,5-diamino-1-ethyl-3-(4′-methoxyphenyl)pyrazole, 4,5-diamino-1-ethyl-3-hydroxymethylpyrazole, 4,5-diamino-3-hydroxymethyl-1-methylpyrazole, 4,5-diamino-3-hydroxymethyl-1-isopropylpyrazole, 4,5-diamino-3-methyl-1-isopropyl-pyrazole, 4-amino-5-(2′-aminoethyl)amino-1,3-dimethyl-pyrazole, 3,4,5-triaminopyrazole, 1-methyl-3,4,5-triaminopyrazole, 3,5-diamino-1-methyl-4-methylaminopyrazole and 3,5-diamino-4-(β-hydroxy-ethyl)amino-1-methylpyrazole, and the addition salts thereof with an acid.

Among the derivatives of pyrazolo[1,2-a]pyrazol-1-one type, mention may be made of compounds such as 2,3-diamino-6,7-dihydro-1H,5H-pyrazolo[1,2-a]pyrazol-1-one.

The composition according to the invention may also contain one or more couplers conventionally used for dyeing keratin fibres. Among these couplers, mention may be made especially of meta-phenylenediamines, meta-aminophenols, meta-diphenols, naphthalene-based couplers and heterocyclic couplers.

Examples that may be mentioned include 2-methyl-5-aminophenol, 5-N-(β-hydroxyethyl)amino-2-methyl-phenol, 6-chloro-2-methyl-5-aminophenol, 3-aminophenol, 1,3-dihydroxybenzene, 1,3-dihydroxy-2-methylbenzene, 4-chloro-1,3-dihydroxybenzene, 2,4-diamino-1-(β-hydroxyethyloxy)benzene, 2-amino-4-(β-hydroxyethyl-amino)-1-methoxybenzene, 1,3-diaminobenzene, 1,3-bis(2,4-diaminophenoxy)propane, 3-ureidoaniline, 3-ureido-1-dimethylaminobenzene, sesamol, 1-β-hydroxy-ethylamino-3,4-methylenedioxybenzene, α-naphthol, 2-methyl-1-naphthol, 6-hydroxyindole, 4-hydroxyindole, 4-hydroxy-N-methylindole, 2-amino-3-hydroxypyridine, 6-hydroxybenzomorpholine, 3,5-diamino-2,6-dimethoxy-pyridine, 1-N-(β-hydroxyethyl)amino-3,4-methylene-dioxybenzene and 2,6-bis(β-hydroxyethylamino)toluene and the addition salts thereof with an acid.

In the composition of the present invention, the oxidation base(s) is (are) generally present in an amount ranging from 0.001% to 10% by weight, and more preferably from 0.005% to 6% by weight, relative to the total weight of the dye composition. The coupler(s) is (are) present in an amount preferably ranging from 0.001% to 10% by weight, and more preferably from 0.005% to 6% by weight, relative to the total weight of the dye composition.

In general, the acid-addition salts that may be used in the context of the dye compositions of the invention for the oxidation bases and couplers are chosen especially from the hydrochlorides, hydrobromides, sulfates, citrates, succinates, tartrates, lactates, tosylates, benzenesulfonates, phosphates and acetates.

The composition according to the invention may optionally comprise at least one additional direct dye other than the compounds of formula (I) or (II). This dye may be chosen from cationic and nonionic species.

Non-limiting examples that may be mentioned include nitrobenzene dyes, azo, azomethine, methine, tetraazapentamethine, anthraquinone, naphthoquinone, benzoquinone, phenothiazine, indigoid, xanthene, phenanthridine, phthalocyanin and triarylmethane-based dyes and natural dyes, alone or as mixtures.

It may be chosen, for example, from the following red or orange nitrobenzene dyes:

-   1-hydroxy-3-nitro-4-N-(γ-hydroxypropyl)aminobenzene, -   N-(β-hydroxyethyl)amino-3-nitro-4-aminobenzene, -   1-amino-3-methyl-4-N-(β-hydroxyethyl)amino-6-nitro-benzene, -   1-hydroxy-3-nitro-4-N-(β-hydroxyethyl)aminobenzene, -   1,4-diamino-2-nitrobenzene, -   1-amino-2-nitro-4-methylaminobenzene, -   N-(β-hydroxyethyl)-2-nitro-para-phenylenediamine, -   1-amino-2-nitro-4-(β-hydroxyethyl)amino-5-chloro-benzene, -   2-nitro-4-aminodiphenylamine, -   1-amino-3-nitro-6-hydroxybenzene, -   1-(β-aminoethyl)amino-2-nitro-4-(β-hydroxyethyloxy)-benzene, -   1-(β,γ-dihydroxypropyl)oxy-3-nitro-4-(β-hydroxy-ethyl)aminobenzene, -   1-hydroxy-3-nitro-4-aminobenzene, -   1-hydroxy-2-amino-4,6-dinitrobenzene, -   1-methoxy-3-nitro-4-(β-hydroxyethyl)aminobenzene, -   2-nitro-4′-hydroxydiphenylamine, and -   1-amino-2-nitro-4-hydroxy-5-methylbenzene.

The additional direct dye may also be chosen from yellow and green-yellow nitrobenzene direct dyes; mention may be made, for example, of the compounds chosen from:

-   1-β-hydroxyethyloxy-3-methylamino-4-nitrobenzene, -   1-methylamino-2-nitro-5-(β,γ-dihydroxypropyl) oxy-benzene, -   1-(β-hydroxyethyl)amino-2-methoxy-4-nitrobenzene, -   1-(β-aminoethyl)amino-2-nitro-5-methoxybenzene, -   1,3-di(β-hydroxyethyl)amino-4-nitro-6-chlorobenzene, -   1-amino-2-nitro-6-methylbenzene, -   1-(β-hydroxyethyl)amino-2-hydroxy-4-nitrobenzene, -   N-(β-hydroxyethyl)-2-nitro-4-trifluoromethylaniline, -   4-(β-hydroxyethyl)amino-3-nitrobenzenesulfonic acid, -   4-ethylamino-3-nitrobenzoic acid, -   4-(β-hydroxyethyl)amino-3-nitrochlorobenzene, -   4-(β-hydroxyethyl)amino-3-nitromethylbenzene, -   4-(β,γ-dihydroxypropyl)amino-3-nitrotrifluoromethyl-benzene, -   1-(β-ureidoethyl)amino-4-nitrobenzene, -   1,3-diamino-4-nitrobenzene, -   1-hydroxy-2-amino-5-nitrobenzene, -   1-amino-2-[tris(hydroxymethyl)methyl]amino-5-nitro-benzene, -   1-(β-hydroxyethyl)amino-2-nitrobenzene, and -   4-(β-hydroxyethyl)amino-3-nitrobenzamide.

Mention may also be made of blue or violet nitrobenzene direct dyes, for instance:

-   1-(β-hydroxyethyl)amino-4-N,N-bis(β-hydroxyethyl)-amino-2-nitrobenzene, -   1-(γ-hydroxypropyl)amino-4-N,N-bis(β-hydroxyethyl)-amino-2-nitrobenzene, -   1-(β-hydroxyethyl)amino-4-(N-methyl-N-β-hydroxy-ethyl)amino-2-nitrobenzene, -   1-(β-hydroxyethyl)amino-4-(N-ethyl-N-p-hydroxy-ethyl)amino-2-nitrobenzene, -   1-(β,γ-dihydroxypropyl)amino-4-(N-ethyl-N-p-hydroxy-ethyl)amino-2-nitrobenzene, -   2-nitro-para-phenylenediamines having the following formula:

in which:

-   -   R_(B) represents a C₁-C₄ alkyl radical or a β-hydroxy-ethyl,         β-hydroxypropyl or γ-hydroxypropyl radical;     -   R_(A) and R_(C), which may be identical or different, represent         a β-hydroxyethyl, β-hydroxypropyl, γ-hydroxy-propyl or         β,γ-dihydroxypropyl radical, at least one of the radicals R_(B),         R_(c) or R_(A) representing a γ-hydroxypropyl radical and R_(B)         and R_(c) not simultaneously being able to denote a         β-hydroxyethyl radical when R_(B) is a γ-hydroxy-propyl radical,         such as those described in French patent FR 2 692 572.

Among the azo direct dyes that may be used according to the invention, mention may be made of the cationic azo dyes described in patent applications WO 95/15144, WO 95/01772, EP 714 954, FR 2 822 696, FR 2 825 702, FR 2 825 625, FR 2 822 698, FR 2 822 693, FR 2 822 694, FR 2 829 926, FR 2 807 650, WO 02/078 660, WO 02/100 834, WO 02/100 369 and FR 2 844 269.

Among these compounds, mention may be made most particularly of the following dyes:

-   1,3-dimethyl-2-[[4-(dimethylamino)phenyl]azo]-1H-imidazolium     chloride, -   1,3-dimethyl-2-[(4-aminophenyl)azo]-1H-imidazolium chloride, -   1-methyl-4-[(methylphenylhydrazono)methyl]-pyridinium methyl     sulfate.

Among the azo direct dyes that may also be mentioned are the following dyes described in the Colour Index International 3rd edition:

-   -   Disperse Red 17     -   Acid Yellow 9     -   Acid Black 1     -   Basic Red 22     -   Basic Red 76     -   Basic Yellow 57     -   Basic Brown 16     -   Acid Yellow 36     -   Acid Orange 7     -   Acid Red 33     -   Acid Red 35     -   Basic Brown 17     -   Acid Yellow 23     -   Acid Orange 24     -   Disperse Black 9.

Mention may also be made of 1-(4′-aminodiphenylazo)-2-methyl-4-[bis(β-hydroxyethyl)amino]benzene and 4-hydroxy-3-(2-methoxyphenylazo)-1-naphthalenesulfonic acid.

Among the quinone direct dyes that may be mentioned are the following dyes:

-   -   Disperse Red 15     -   Solvent Violet 13     -   Acid Violet 43     -   Disperse Violet 1     -   Disperse Violet 4     -   Disperse Blue 1     -   Disperse Violet 8     -   Disperse Blue 3     -   Disperse Red 11     -   Acid Blue 62     -   Disperse Blue 7     -   Basic Blue 22     -   Disperse Violet 15     -   Basic Blue 99 and also the following compounds:

-   1-N-methylmorpholiniumpropylamino-4-hydroxyanthra-quinone

-   1-aminopropylamino-4-methylaminoanthraquinone

-   1-aminopropylaminoanthraquinone

-   5-p-hydroxyethyl-1,4-diaminoanthraquinone

-   2-aminoethylaminoanthraquinone

-   1,4-bis(β,γ-dihydroxypropylamino) anthraquinone.

Among the azine dyes that may be mentioned are the following compounds:

-   -   Basic Blue 17     -   Basic Red 2.

Among the triarylmethane dyes that may be used according to the invention, mention may be made of the following compounds:

-   -   Basic Green 1     -   Acid Blue 9     -   Basic Violet 3     -   Basic Violet 14     -   Basic Blue 7     -   Acid Violet 49     -   Basic Blue 26     -   Acid Blue 7.

Among the indoamine dyes that may be used according to the invention, mention may be made of the following compounds:

-   2-β-hydroxyethylamino-5-[bis(β-4′-hydroxyethyl)-amino]anilino-1,4-benzoquinone; -   2-p-hydroxyethylamino-5-(2′-methoxy-4′-amino)-anilino-1,4-benzoquinone; -   3-N(2′-chloro-4′-hydroxy)phenylacetylamino-6-methoxy-1,4-benzoquinoneimine; -   3-N(3′-chloro-4′-methylamino)phenylureido-6-methyl-1,4-benzoquinoneimine; -   3-[4′-N-(ethylcarbamylmethyl)amino]phenylureido-6-methyl-1,4-benzoquinoneimine.

Among the dyes of tetraazapentamethine type that may be used according to the invention, mention may be made of the following compounds:

-   2-((E)-{(E)-[(1,3-dimethyl-1,3-dihydro-2H-imidazol-2-ylidene)hydrazono]methyl}diazenyl)-1,3-dimethyl-1H-imidazol-3-ium     chloride; -   2-{(E)-[(1Z)-N-(1,3-dimethyl-1,3-dihydro-2H-imidazol-2-ylidene)ethanehydrazonoyl]diazenyl}-1,3-dimethyl-1H-imidazol-3-ium     chloride; -   4-methoxy-2-((E)-{(1E)-1-[(2E)(4-methoxy-1-methyl-pyridin-2(1H)-ylidene)hydrazono]ethyl}diazenyl)-1-methylpyridinium     chloride; -   1-methyl-2-((E)-{(1E)-1-[(2E)(1-methylpyridin-2(1H)—ylidene)hydrazono]ethyl}diazenyl)pyridinium     chloride; -   1-(2-hydroxyethyl)-2-[(E)((1E)-1-{(2E)[1-(2-hydroxy-ethyl)pyridin-2(1H)-ylidene]hydrazono}ethyl)diazenyl]-pyridinium     chloride; -   1-methyl-2-((E){(E)[(2Z)(1-methylpyridin-2(1H)-ylidene)hydrazono]methyl}diazenyl)pyridinium     chloride; -   1-(2-hydroxyethyl)-2-[(E)((E){(2E)[1-(2-hydroxy-ethyl)pyridin-2(1H)-ylidene]hydrazono}methyl)diazenyl]-pyridinium     chloride.

Among the natural direct dyes that may be used according to the invention, mention may be made of lawsone, juglone, alizarin, purpurin, carminic acid, kermesic acid, purpurogallin, protocatechaldehyde, indigo, isatin, curcumin, spinulosin and apigenidin. Extracts or decoctions containing these natural dyes may also be used, and especially henna-based poultices or extracts.

When they are present, the content of additional direct dye(s) in the composition generally ranges from 0.001% to 20% by weight relative to the weight of the composition and preferably from 0.01% to 10% by weight relative to the weight of the composition.

The medium that is suitable for dyeing, also known as the dye support, generally consists of water or of a mixture of water and of at least one organic solvent to dissolve the compounds that are not sufficiently water-soluble.

More particularly, the organic solvents are chosen from linear or branched, preferably saturated monoalcohols or diols containing from 2 to 10 carbon atoms, such as ethyl alcohol, isopropyl alcohol, hexylene glycol (2-methyl-2,4-pentanediol), neopentyl glycol and 3-methyl-1,5-pentanediol; aromatic alcohols such as benzyl alcohol and phenylethyl alcohol; glycols or glycol ethers, for instance ethylene glycol monomethyl, monoethyl and monobutyl ether, propylene glycol and its ethers, for instance propylene glycol monomethyl ether, butylene glycol and dipropylene glycol; and also diethylene glycol alkyl ethers, especially of C₁-C₄, for instance diethylene glycol monoethyl ether or monobutyl ether, alone or as a mixture.

The usual solvents described above, when they are present, usually represent from 1% to 40% by weight and more preferably from 5% to 30% by weight relative to the total weight of the composition.

The dye composition in accordance with the invention may also contain various adjuvants conventionally used in compositions for dyeing the hair, such as anionic, cationic, nonionic, amphoteric or zwitterionic surfactants or mixtures thereof, anionic, cationic, nonionic, amphoteric or zwitterionic polymers or mixtures thereof, mineral or organic thickeners, and in particular anionic, cationic, nonionic and amphoteric associative polymeric thickeners, antioxidants, penetrants, sequestrants, fragrances, buffers, dispersants, conditioning agents, for instance silicones, which may or may not be volatile or modified, film-forming agents, ceramides, preserving agents and opacifiers.

The above adjuvants are generally present in an amount for each of them of between 0.01% and 20% by weight relative to the weight of the composition.

Needless to say, a person skilled in the art will take care to select this or these optional additional compounds such that the advantageous properties intrinsically associated with the oxidation dye composition in accordance with the invention are not, or are not substantially, adversely affected by the envisaged addition(s).

The pH of the dye composition in accordance with the invention is generally between about 3 and 12 and preferably between about 5 and 11. It may be adjusted to the desired value using acidifying or basifying agents usually used in the dyeing of keratin fibres, or alternatively using standard buffer systems.

Among the acidifying agents that may be mentioned, for example, are mineral or organic acids such as hydrochloric acid, orthophosphoric acid, sulfuric acid, carboxylic acids such as acetic acid, tartaric acid, citric acid and lactic acid, and sulfonic acids.

Among the basifying agents that may be mentioned, for example, are aqueous ammonia, alkaline carbonates, alkanolamines such as monoethanolamine, diethanolamine and triethanolamine and derivatives thereof, sodium hydroxide, potassium hydroxide and the compounds having the following formula:

in which W is a propylene residue optionally substituted with a hydroxyl group or a C₁-C₄ alkyl radical; R_(D), R_(E), R_(F) and R_(G), which may be identical or different, represent a hydrogen atom, a C₁-C₄ alkyl radical or a C₁-C₄ hydroxyalkyl radical.

The dye composition according to the invention may be in various forms, such as in the form of liquids, creams or gels, or in any other form that is suitable for dyeing keratin fibres, and especially human hair.

The composition according to the invention may also comprise at least one oxidizing agent to allow simultaneous lightening.

The oxidizing agent may be any oxidizing agent conventionally used in the field. Thus, it may be chosen from hydrogen peroxide, urea peroxide, alkali metal bromates, persalts such as perborates and persulfates, and also enzymes, among which mention may be made of peroxidases, 2-electron oxidoreductases such as uricases, and 4-electron oxygenases, for instance laccases.

A subject of the invention is also a dyeing process that comprises the application of a dye composition according to the invention to wet or dry keratin fibres, for a leave-on time that is sufficient to obtain the desired coloration.

When the oxidizing agent is present, it may be added to the composition comprising the compound(s) of formula (I) at the time of use, or may be applied directly to the keratin fibre.

Whatever the variant adopted (with or without oxidizing agent), the leave-in time is generally between a few seconds and 30 minutes and preferably between 3 and 15 minutes.

The temperature at which the composition is left to act is generally between 15 and 220° C., more particularly between 15 and 80° C. and preferably between 15 and 40° C.

After the leave-in time, the composition is removed by rinsing with water, optionally followed by washing with a shampoo, and then optionally drying.

Another subject of the invention is a multi-compartment device or dyeing “kit” in which a first compartment contains the dye composition of the invention and a second compartment contains the oxidizing composition. This device may be equipped with a means for applying the desired mixture to the hair, such as the devices described in patent FR-2 586 913.

A subject of the present invention is also the direct dyes of formula (I) or (II) as defined above, with the exception of the compound having the following formula:

and also the mesomeric forms thereof, the acid-addition salts thereof and the solvates thereof.

The examples that follow serve to illustrate the invention without, however, being limiting in nature.

EXAMPLES Examples of Synthesis

A mixture of monoazo dye (2.16 g), of concentrated hydrochloric acid (2 mL), of acetic acid (1 mL) and of water (15 mL) is cooled to 5° C. and a solution of sodium nitrite (0.8 g) dissolved in water (2 mL) is then added dropwise, while maintaining a temperature of less than 5° C. After 30 minutes, urea (0.1 g) is added, and the diazonium salt solution thus obtained is then added dropwise to a solution of N,N-dimethylaniline (1.2 g), water (15 mL), ethanol (5 mL) and sodium hydrogen-carbonate (1.08 g), while maintaining a temperature of less than 5° C. After stirring for one hour, the solution is brought to pH 7 with aqueous NaHCO₃ solution and the temperature is allowed to rise to room temperature. The solution is evaporated under vacuum to a quarter of its volume. The remaining solution is poured into acetone (200 mL) and the precipitate obtained is then filtered off. It is dried under vacuum for four days at 40° C. 2.6 g of brown crystals are thus obtained. The analyses indicate that dye 1 has indeed been obtained (NMR, HPLC, MS).

A mixture of monoazo dye (2.16 g), of concentrated hydrochloric acid (2 mL), of acetic acid (1 mL) and of water (15 mL) is cooled to 5° C. and a solution of sodium nitrite (0.8 g) in water (2 mL) is then added dropwise, while maintaining a temperature of less than 5° C. After stirring for 30 minutes at 0° C., urea (0.1 g) is added and the diazonium salt solution thus obtained is then poured into a solution containing ethylaminocresol (1.51 g), water (25 mL), ethanol (30 mL) and sodium hydrogencarbonate (1.08 g), while maintaining a temperature of less than 5° C. After stirring for one hour, the pH is brought to 7 with aqueous NaHCO₃ solution and the temperature is allowed to rise to room temperature. The solution is evaporated under vacuum to a quarter of its volume. The solution is poured into 300 ml of acetone. A precipitate is obtained. This precipitate is filtered off and then dried under vacuum. 1.6 g of black crystals are thus obtained. The analyses indicate that dye 2 has indeed been obtained (NMR, HPLC, MS).

A mixture consisting of 3-chloro-4-(dimethyl-amino)aniline (7 g), of 5N hydrochloric acid (22 mL) and of water (54 mL) is cooled to 5° C. and a solution consisting of sodium nitrite (2.83 g) dissolved in water (28 mL) is then added dropwise, while maintaining a temperature of less than 5° C. After stirring for one hour, sulfamic acid (0.1 g) is added and the diazonium salt solution obtained previously is then added dropwise to a solution of 5-methyl-2-methoxyaniline (5.92 g) dissolved in water (14 mL) and acetic acid (28 mL), while maintaining a temperature of less than 5° C. After stirring for two hours at room temperature, the pH is brought to 8-9 with aqueous 4M K₂CO₃ solution. After stirring for one hour at 0-5° C., water (600 mL) is added. The aqueous phase is extracted with dichloro-methane (4×200 mL) and the organic phases are then combined. The resulting organic phase is dried over Na₂SO₄, filtered and then concentrated under vacuum. 14.2 g of brown powder are obtained. This powder is purified by chromatography on silica-60 gel using a heptane/ethyl acetate mixture as eluent. 9.33 g of pure product are thus obtained. The analyses indicate that the expected product has indeed been obtained (NMR, HPLC, MS).

A solution of sodium nitrite (0.108 g) dissolved in water (1 mL) is added dropwise to the product obtained previously (0.509 g) predissolved in 5N hydrochloric acid (3 mL) and acetonitrile (8 mL), while maintaining a temperature of less than 5° C.

After 30 minutes, sulfamic acid (0.1 g) is added, followed by addition of a solution containing imidazole (0.108 g) dissolved in water (1 mL). After stirring for two hours at room temperature, the pH is brought to 8-9 with aqueous 4M K₂CO₃ solution. After stirring for one hour, water is added. The aqueous phase is extracted with dichloromethane (3×75 mL). The organic phases are combined and then dried over Na₂SO₄. After filtration, the organic phase is concentrated under vacuum. 616 mg of brown-yellow powder are obtained. This powder is then purified by chromatography on silica-60 gel, using a dichloromethane/methanol mixture as eluent. 332 mg of pure product are thus obtained. The analyses indicate that the expected product has indeed been obtained (NMR, HPLC, MS)

Dimethyl sulfate (66.6 mg) is added to the product obtained previously (100 mg) dissolved in THF (2 mL) and in the presence of sodium acetate (22.7 mg), and the reaction mixture is then stirred at 65° C. for three hours. The reaction medium is then concentrated by distilling off the solvents under vacuum, and the oil obtained (186 mg) is then purified by chromatography on silica-60 gel, using the dichloromethane/methanol binary system as eluent. 82 mg of pure product are thus obtained. The analyses indicate that the expected product has indeed been obtained (NMR, HPLC).

¹H NMR (300 MHz, MeOD, δ ppm): 2.70 (3H, s); 3.01 (6H, s); 3.70 (3H, s); 4.10 (3H, s); 4.18 (6H, s); 7.28 (1H, s); 7.48 (1H, s); 7.79 (2H, s); 7.89 (1H, s); 7.97 (1H, d); 8.00 (1H, s).

MS (ESI⁺): M⁺=426.13.

A mixture containing 2-aminoimidazole sulfate (9.63 g), sulfuric acid (29 mL) and water (38 mL) is cooled to 5° C. and a solution consisting of sodium nitrite (5.53 g) dissolved in water (15 mL) is then added dropwise, while maintaining a temperature of less than 5° C. After stirring for one hour, sulfamic acid (0.1 g) is added and the diazonium salt solution obtained is then added dropwise to a solution consisting of 5-methoxy-2-methylaniline (10 g) and glacial acetic acid (50 mL), while maintaining the reaction medium at a temperature below 5° C. After stirring for four hours at room temperature, the pH is brought to 7-8 with aqueous Na₂CO₃ solution. A paste forms. After separation of the phases by settling, the liquors are removed and the paste is dissolved in ethanol and then dried over Na₂SO₄, filtered and finally concentrated under vacuum. 17.2 g of red powder are obtained.

The product is taken up in acetone. The insoluble matter is filtered off and then dried under vacuum. 15.9 g of red powder are thus obtained. The analyses indicate that the expected product has indeed been obtained (NMR, HPLC)

Sulfuric acid (12 mL) and water (20 mL) are added to the product obtained in the preceding step (2 g). The reaction medium is cooled to 0-5° C. and a solution of sodium nitrite (0.656 g) dissolved in water (2 mL) is then added dropwise to the reaction medium, while maintaining a temperature of less than 5° C. After reaction for one hour, sulfamic acid (0.1 g) is added, followed by dropwise addition of a solution of N,N-dimethylaminophenol (1.19 g) dissolved in glacial acetic acid (6 mL), while maintaining a temperature of less than 5° C. After stirring for two hours at 0-5° C., the reaction mixture is poured onto ice and the pH is brought to 8 with aqueous Na₂CO₃ solution. A precipitate forms. This precipitate is filtered off, rinsed with water and then with diethyl ether and finally dried under vacuum in the presence of P₂O₅. 1.82 g of a violet-blue powder are obtained. This powder is purified by chromatography on silica-60 gel, using the dichloromethane/methanol binary mixture as eluent. 546 mg of violet powder are thus obtained. The HPLC purity is greater than 99%.

The product obtained in the preceding step (385 mg) is dissolved in THF (23 mL) in the presence of sodium acetate (91.6 mg). Dimethyl sulfate (269 mg) is added and the reaction mixture is then stirred at 65° C. for three hours. The reaction medium is then cooled to room temperature. The precipitate obtained is filtered off, rinsed with ethyl acetate and then dried under vacuum. The solid obtained is recrystallized from a mixture consisting of methanol/tert-butyl methyl ether. After filtration, and then drying under vacuum, 155 mg of a violet powder are obtained. This new powder is taken up again in pentane, filtered off and then dried under vacuum. 137 mg of violet powder are thus obtained. The HPLC purity is greater than 99%.

A mixture consisting of 4-nitro-2-chloroaniline (3.5 g), of 1N hydrochloric acid solution (90 mL) and of acetonitrile (50 mL) is cooled to 5° C. and a solution of sodium nitrite (1.41 g) dissolved in water (15 mL) is then added dropwise, while maintaining a temperature of less than 5° C. After reaction for 30 minutes, sulfamic acid (0.1 g) is added and the mixture is then poured into a solution consisting of N,N-dimethyl-aniline (2.68 mL), 1N hydrochloric acid (80 mL) and acetonitrile (80 mL), while maintaining the reaction medium at a temperature below 5° C. After stirring for 1.5 hours at 0-5° C., the pH is brought to 12 with aqueous 4M K₂CO₃ solution. After stirring for one hour at 0-5° C., water (600 mL) is added. The aqueous phase is extracted with dichloromethane (3×400 mL). The organic phases obtained are combined, dried over Na₂SO₄, filtered and then evaporated. 5 g of black powder are obtained. This powder is purified by chromatography on silica gel (40-60 μm) using the heptane/ethyl acetate binary mixture as eluent. 1.89 g of pure product are thus obtained. The analyses indicate that the expected product has indeed been obtained (NMR, HPLC).

The product obtained in the preceding step (0.5 g) is dissolved in ethanol (50 mL). Sodium sulfite monohydrate (0.79 g) is added, and the reaction mixture is then stirred at reflux for one hour. The reaction medium is then concentrated by distillation under vacuum, and the residue thus obtained is dissolved in water. The aqueous phase is extracted with dichloromethane and then dried over Na₂SO₄, filtered and evaporated. 0.4 g of pure product is thus obtained. The analyses indicate that the expected product has indeed been obtained (NMR, MS).

A solution of sodium nitrite (0.113 g) dissolved in water (13 mL) is added dropwise to the product obtained in the preceding step (0.45 g) dissolved in 5N hydrochloric acid (36.5 mL) and acetonitrile (11.5 mL), while maintaining the reaction medium at a temperature below 5° C.

After reaction for 30 minutes, sulfamic acid (0.1 g) is added, followed by addition of a solution consisting of imidazole (0.112 g) dissolved in water (1.2 mL). After stirring for four hours at 0-5° C., the pH is brought to 10 with aqueous 4M K₂CO₃ solution. After stirring for one hour at 0-5° C., water is added. The aqueous phase is extracted with dichloromethane (3×400 mL). The organic phases obtained are combined, dried over Na₂SO₄, filtered and then concentrated under vacuum. 667 mg of crude product are obtained. This product is purified by chromatography on silica-60 gel, using the dichloro-methane/methanol binary mixture as eluent. 233 mg of pure product are thus obtained. The analyses indicate that the expected product has indeed been obtained (NMR, HPLC).

The product obtained in step 3 (233 mg) is dissolved in THF (50 mL) in the presence of sodium acetate (60 mg). Dimethyl sulfate (174 mg) is added and the reaction mixture is then stirred at 65° C. for two hours. The reaction medium is then concentrated by distilling off the solvents under vacuum, and the residue thus obtained is purified by chromatography on silica-60 gel, using the dichloromethane/methanol binary mixture as eluent. 215 mg of product are thus obtained. A second purification step consists in reslurrying the product in heptane for 45 minutes. After filtration and then drying under vacuum, 150 mg of pure product are obtained. The analyses indicate that the expected product has indeed been obtained (NMR, HPLC).

¹H NMR (300 MHz, MeOD, δ ppm): 3.18 (6H, s); 3.65 (4H, s); 4.15 (6H, s); 6.84 (2H, d); 7.73-8.18 (7H, m).

MS (ESI⁺): M⁺=382.16.

A mixture consisting of monoazo dye (2.5 g), of concentrated hydrochloric acid (2.5 mL), of acetic acid (2 mL) and of water (38 mL) is cooled to 5° C. and a solution of sodium nitrite (0.8 g) dissolved in water (2 mL) is then added dropwise, while maintaining the reaction medium at a temperature below 5° C. After reaction for 30 minutes, urea (0.1 g) is added. The diazonium salt solution obtained previously is poured dropwise into a solution consisting of julolidine (1.73 g) dissolved in water (25 mL) and ethanol (10 mL) in the presence of sodium hydrogencarbonate (2 g), while taking care to maintain the reaction medium at a temperature below 5° C. After stirring for one hour, the pH is brought to 7 with aqueous NaHCO₃ solution and the temperature is allowed to return to room temperature. The solution is evaporated under vacuum. The residue obtained is purified by chromatography on silica-60 gel, using the dichloromethane/methanol binary mixture as eluent. After evaporation under vacuum, 450 mg of blue powder are thus obtained. The analyses indicate that the expected product has indeed been obtained (NMR, HPLC, MS).

Examples of Dyeing

The following dye compositions are prepared:

Composition 1 2 Dye 1 10⁻³ mol 10⁻³ mol Dye support (1) (2) Dye support (1), pH = 7: 96° ethyl alcohol 20.8 g Pentasodium salt of diethylenetriamine- 0.48 g AM pentaacetic acid as an aqueous 40% solution C₈-C₁₀ alkyl polyglucoside as an aqueous 3.6 g AM 60% solution Benzyl alcohol 2.0 g Polyethylene glycol containing 8 ethylene 3.0 g oxide units Na₂HPO₄ 0.28 g KH₂PO₄ 0.46 g Dye support (2), pH = 9.5: 96° ethyl alcohol 20.8 g Pentasodium salt of diethylenetriamine- 0.48 g AM pentaacetic acid as an aqueous 40% solution C₈-C₁₀ alkyl polyglucoside as an aqueous 3.6 g AM 60% solution Benzyl alcohol 2.0 g Polyethylene glycol containing 8 ethylene 3.0 g oxide units NH₄Cl 4.32 g Aqueous ammonia containing 20% NH₃ 2.94 g

For the colorations performed under non-lightening conditions (without oxidizing agent), these compositions are applied directly to the hair.

For the colorations performed under lightening conditions, an oxidizing medium is used. In this case, at the time of use, each composition is mixed with an equal weight of 20-volumes aqueous hydrogen peroxide solution (6% by weight). A final pH equal to 7 and to 9.5, respectively, is obtained.

Each composition with or without oxidizing agent is applied to locks of grey hair containing 90% white hairs, at a rate of 6 g of composition per 1 g of hair. After a leave-on time of 30 minutes, the locks are rinsed, washed with a standard shampoo, rinsed again and then dried.

The following dyeing results were obtained.

pH 7 pH 9.5 pH 7 pH 9.5 (without (without (with (with oxidizing oxidizing oxidizing oxidizing agent) agent) agent) agent) Dye 1 Sparingly Sparingly Sparingly Sparingly chromatic chromatic chromatic chromatic blue blue blue blue Dye 2 Sparingly Sparingly Sparingly Sparingly chromatic chromatic chromatic chromatic blue blue blue blue Dye 3 Sparingly Sparingly Sparingly Sparingly chromatic chromatic chromatic chromatic violet violet violet violet Dye 4 Sparingly Sparingly Sparingly Sparingly chromatic chromatic chromatic chromatic blue blue blue blue Dye 5 Sparingly Sparingly Sparingly Sparingly chromatic chromatic chromatic chromatic violet violet violet violet Dye 6 Blue Blue Blue Blue

The locks thus dyed are subjected to a wash-fastness test, which consists in shampooing 12 times (with a standard shampoo) and evaluating the colour after these 12 shampoo washes. After 12 shampoo washes, the locks are still coloured. 

1-34. (canceled)
 35. A composition for dyeing keratin fibers, comprising, in a suitable dyeing medium, at least one cationic diazo direct dye comprising a 2-imidazolium unit, chosen from the compounds of formula (I) and (II) below, the mesomeric forms thereof, and the acid-addition salts thereof:

wherein: the radicals R₁ independently of each other, are chosen from: a linear or branched, saturated, acyclic, optionally substituted C₁-C₈ hydrocarbon-based chain, optionally interrupted with at least one heteroatom and/or with at least one group comprising at least one heteroatom, wherein the at least one heteroatom is chosen from oxygen, nitrogen, sulfur, CO, SO, and SO₂, or combinations thereof; and wherein the hydrocarbon-based chain when attached to the nitrogen atom of the imidazolium ring does not comprise nitro, nitroso, peroxo, or diazo functions; an optionally substituted phenyl radical; and an optionally substituted benzyl radical; the radicals R₂, independently of each other are chosen from: a linear C₁-C₄ alkyl radical, optionally substituted with an amino radical or a hydroxyl radical; an optionally substituted phenyl radical; and a halogen atom; the radicals R₃, independently of each other are chosen from: a linear C₁-C₄ alkyl radical, optionally substituted with an amino radical or a hydroxyl radical; a hydroxyl radical; a C₁-C₄ alkoxy radical; a C₁-C₄ monohydroxyalkoxy or polyhydroxyalkoxy radical; an amino radical optionally substituted with one or two C₁-C₄ alkyl radicals, which may be identical or different, optionally bearing at least one hydroxyl radical; a group R_(a)CO—NR_(a)′— in which the radical R_(a) is chosen from a C₁-C₄ alkyl radical and the radical R_(a)′ is chosen from a hydrogen atom and a C₁-C₄ alkyl radical; a group (R_(b))₂N—CO— wherein the radicals R_(b) are chosen from, independently of each other, a hydrogen atom and a C₁-C₄ alkyl radical; a group (R_(c))₂N—CO—NR_(c)— in which the radicals R_(c) are chosen from, independently of each other, a hydrogen atom and a C₁-C₄ alkyl radical; a group (R_(d))₂N—SO₂— in which the radicals R_(d) are chosen from, independently of each other, a hydrogen atom and a C₁-C₄alkyl radical; a group R_(e)SO₂—NR_(e)— in which the radicals R_(e) are chosen from, independently of each other, a hydrogen atom and a C₁-C₄ alkyl radical; a cyano radical; and a halogen atom; the radicals R₄ are chosen from, independently of each other: a linear C₁-C₄ alkyl radical; a hydroxyl radical; a C₁-C₄ alkoxy radical; a C₁-C₄ monohydroxyalkoxy or polyhydroxyalkoxy radical; an amino radical optionally substituted with one or two C₁-C₄ alkyl radicals, which may be identical or different, the one or two alkyl radicals optionally bearing at least one hydroxyl radical; the two alkyl radicals optionally forming, together with the nitrogen atom to which they are attached, a 5 or 6-membered heterocycle optionally comprising another heteroatom identical to or different from nitrogen, and optionally substituted with at least one methyl, hydroxyl, amino, monomethylamino or dimethyl amino radicals; a group R_(a)CO—NR_(a)′— wherein the radical R_(a) is chosen from a C₁-C₄ alkyl radical and the radical R_(a)′ is chosen from a hydrogen atom and a C₁-C₄ alkyl radical; a group (R_(b))₂N—CO— wherein the radicals R_(b) are chosen from, independently of each other, a hydrogen atom and a C₁-C₄ alkyl radical; a group (R_(c))₂N—CO—NR_(c)— wherein the radicals R_(c) are chosen from, independently of each other, a hydrogen atom and a C₁-C₄ alkyl radical; a group (R_(d))₂N—SO₂ in which the radicals R_(d) are chosen from, independently of each other, a hydrogen atom and a C₁-C₄ alkyl radical; a group R_(e)SO₂—NR_(e)— wherein the radicals R_(e) are chosen from, independently of each other, a hydrogen atom and a C₁-C₄ alkyl radical; a cyano radical; and a halogen atom; the radicals R₅ and R₆, which may be identical or different, are chosen from: a hydrogen atom; a linear or branched, saturated, acyclic, optionally substituted C₁-C₈ hydrocarbon-based chain, optionally interrupted with at least one heteroatom and/or with at least one group comprising at least one heteroatom, wherein the at least one heteroatom is chosen from oxygen, nitrogen, sulfur, CO, SO, and SO₂, or combinations thereof; and wherein the hydrocarbon-based chain does not comprise nitro, nitroso, peroxo, or diazo functions and being attached to the nitrogen atom via a carbon atom; a radical (R_(f)SO₂—) wherein the radical R_(f) is chosen from a C₁-C₄ alkyl radical; a benzyl radical optionally substituted with at least one hydroxyl and/or amino radicals; the radicals R₅ and R₆ optionally forming, with the nitrogen atom to which they are attached, a saturated or unsaturated, optionally substituted 5- or 7-membered heterocycle, optionally comprising another heteroatom that is identical to or different from nitrogen; one of the radicals R₅ and R₆ optionally forming, with the nitrogen atom to which it is attached and with a radical R₄ located ortho to the group NR₅R₆, an optionally substituted 5- or 6-membered heterocycle of formula (III) below

wherein: o is chosen from 0 and 1; Rx and Ry are chosen from, independently of each other, a hydrogen atom and a methyl radical; the radicals R₅ and R₆ optionally forming, with the nitrogen atom to which they are attached and each with a radical R₄ located ortho to the group NR₅R₆, an optionally substituted 5- or 6-membered heterocycle of formula (IV) below:

wherein: o is chosen from 0 and 1; Rx and Ry are chosen from, independently of each other, a hydrogen atom and a methyl radical; n is chosen from 0, 1, and 2; when n is 0 or 1, the unsubstituted carbon atom bears a hydrogen atom; n′ is chosen from 0, 1, 2, 3, and 4 when n′ is 0, 1, 2, or 3, the unsubstituted carbon atom bears a hydrogen atom; n″ is chosen from 0, 1, 2, 3, and 4 when n″ is 0, 1, 2, or 3, the unsubstituted carbon atom bears a hydrogen atom; and the electrical neutrality of the compounds of formula (I) or (II) being assured by at least one identical or different cosmetically acceptable anions An.
 36. A composition according to claim 35, wherein one of the radicals R₅ or R₆ forms, with the nitrogen atom to which it is attached and with a radical R₄ located ortho to the group NR₅R₆, one of the substituted or unsubstituted, saturated or unsaturated 5- or 6-membered heterocycles having the following formulae:

wherein p is chosen from 0 and
 1. 37. A composition according to claim 35, wherein the radicals R₅ and R₆ form, with the nitrogen atom to which they are attached and each with a radical R₄ located ortho to the group NR₅R₆, an optionally substituted 5- or 6-membered heterocycle of formula (IV) below:

wherein: o is chosen from 0 and 1; and Rx and Ry are chosen from, independently of each other, a hydrogen atom and a methyl radical.
 38. A composition according to claim 35, wherein the radicals R₅ and R₆ form, together with the nitrogen atom to which they are attached and each with a radical R₄ located ortho to the group NR₅R₆, one of the substituted or unsubstituted, saturated or unsaturated 5- or 6-membered heterocycles having the following formulae:

wherein p is chosen from 0 and
 1. 39. A composition according to claim 35, wherein An is chosen from halides; hydroxide; sulfates; hydrogen sulfates; alkyl sulfates for which the linear or branched alkyl part is of C₁-C₆; carbonates; hydrogen carbonates; carboxylic acid salts; alkylsulfonates for which the linear or branched alkyl part is of C₁-C₆; arylsulfonates for which the aryl part is optionally substituted with at least one C₁-C₄ alkyl radical; and alkylsulfonyl.
 40. A composition according to claim 35, wherein the said direct dye of formula (I) and (II) are chosen from the direct dyes of formula (I′) and (II′) below:

wherein: the radicals R′₁, are chose from, independently of each other, a C₁-C₄ alkyl radical and a 2-hydroxyethyl radical; the radicals R′₃ are chosen from, independently of each other, a C₁-C₄ alkyl radical; a C₁-C₄ alkoxy radical; a halogen atom; a hydroxyl radical; and a methylcarbonylamino radical; m′ is chosen from 0, 1 and 2; the radicals R′₄ is chosen from, independently of each other, a C₁-C₄ alkyl radical; a hydroxyl radical; an alkoxy radical; a mono(alkyl)amino radical, a di(alkyl)amino radical; a di(hydroxyalkyl)amino radical; a halogen atom; and a (C₁-C₄) alkylcarbonylamino radical; m″ is chosen from 0, 1, 2 and 3; the radicals R₁₅ and R₁₆ are chosen from, independently of each other, a C₁-C₄ alkyl radical; and a C₁-C₄ mono-hydroxyalkyl radical; or form, with one or two radicals R′₄ located ortho to the group NR₁₅R₁₆ and the benzene nucleus to which they are attached, a ring of formula (III) and (IV).
 41. A composition according to claim 35 wherein the said direct dye of formula (I) is chosen from the compounds presented in the table below, Dye 1

Dye 2

Dye 3

Dye 4

Dye 5

Dye 6

Dye 7

Dye 8

Dye 9

Dye 10

Dye 11

wherein An is chosen from halides; hydroxide; sulfates; hydrogen sulfates; alkyl sulfates for which the linear or branched alkyl part is of C₁-C₆; carbonates; hydrogen carbonates, carboxylic acid salts; alkylsulfonates for which the linear or branched alkyl part is of C₁-C₆; arylsulfonates for which the aryl part is optionally substituted with at least one C₁-C₄ alkyl radical and alkylsulfonyls:
 42. A composition according to claim 35, wherein the said direct dye is is present in an amount ranging from 0.01% to 5% by weight relative to the total weight of the composition.
 43. A composition according to claim 35, further comprising at least one oxidation base chosen from para-phenylenediamines, bis(phenyl)alkylene-diamines, para-aminophenols, ortho-aminophenols, and heterocyclic bases.
 44. A composition according to claim 43, wherein the oxidation base is present in an amount ranging from 0.001% to 10% by weight relative to the total weight of the composition.
 45. A composition according to claim 35, further comprising at least one coupler chosen from metaphenylenediamines, meta-aminophenols, meta-diphenols, naphthalene-based couplers, and heterocyclic couplers.
 46. A composition according to claim 45, wherein the coupler is present in an amount ranging from 0.001% to 10% by weight relative to the total weight of the composition.
 47. A composition according to claim 35, further comprising an additional direct dye is chosen from nitrobenzene dyes, azo, azomethine, methine, tetraazapentamethine, anthraquinone, naphthoquinone, benzoquinone, phenothiazine, indigoid, xanthene, phenanthridine, phthalocyanin and triarylmethane-based dyes, and natural dyes, alone or as mixtures.
 48. A composition according to claim 47, wherein the said additional direct dye is present in an amount ranging from 0.001% to 20% by weight approximately relative to the total weight of the composition.
 49. A composition according to claim 35, wherein the composition further comprises at least one additive chosen from anionic, cationic, nonionic, amphoteric or zwitterionic surfactants or mixtures thereof, anionic, cationic, nonionic, amphoteric or zwitterionic polymers or mixtures thereof, mineral or organic thickeners, antioxidants, penetrants, sequestrants, fragrances, buffers, dispersants, conditioning agents, film-forming agents, ceramides, preserving agents, stabilizers, and opacifiers.
 50. A composition according to claim 35, further comprising at least one oxidizing agent.
 51. A composition according to claim 50, wherein the oxidizing agent is chosen from hydrogen peroxide, urea peroxide, alkali metal bromates, persalts, and enzymes.
 52. A process for dyeing keratin fibers that comprises placing a composition in contact with the said wet or dry fibers, for a time that is sufficient to obtain the desired effect, the composition for dyeing keratin fibers, comprising, in a suitable dyeing medium, at least one cationic diazo direct dye comprising a 2-imidazolium unit, chosen from the compounds of formula (I) and (II) below, the mesomeric forms thereof, and the acid-addition salts thereof:

wherein: the radicals R₁ independently of each other, are chosen from: a linear or branched, saturated, acyclic, optionally substituted C₁-C₈ hydrocarbon-based chain, optionally interrupted with at least one heteroatom and/or with at least one group comprising at least one heteroatom, wherein the at least one heteroatom is chosen from oxygen, nitrogen, sulfur, CO, SO, and SO₂, or combinations thereof; and wherein the hydrocarbon-based chain when attached to the nitrogen atom of the imidazolium ring does not comprise nitro, nitroso, peroxo, or diazo functions; an optionally substituted phenyl radical; and an optionally substituted benzyl radical; the radicals R₂, independently of each other are chosen from: a linear C₁-C₄ alkyl radical, optionally substituted with an amino radical or a hydroxyl radical; an optionally substituted phenyl radical; and a halogen atom; the radicals R₃, independently of each other are chosen from: a linear C₁-C₄ alkyl radical, optionally substituted with an amino radical or a hydroxyl radical; a hydroxyl radical; a C₁-C₄ alkoxy radical; a C₁-C₄ monohydroxyalkoxy or polyhydroxyalkoxy radical; an amino radical optionally substituted with one or two C₁-C₄ alkyl radicals, which may be identical or different, optionally bearing at least one hydroxyl radical; a group R_(a)CO—NR_(a)′— in which the radical R_(a) is chosen from a C₁-C₄ alkyl radical and the radical R_(a)′ is chosen from a hydrogen atom and a C₁-C₄ alkyl radical; a group (R_(b))₂N—CO— wherein the radicals R_(b) are chosen from, independently of each other, a hydrogen atom and a C₁-C₄ alkyl radical; a group (R_(c))₂N—CO—NR_(c)— in which the radicals R_(c) are chosen from, independently of each other, a hydrogen atom and a C₁-C₄ alkyl radical; a group (R_(d))₂N—SO₂— in which the radicals R_(d) are chosen from, independently of each other, a hydrogen atom and a C₁-C₄ alkyl radical; a group R_(e)SO₂—NR_(e)— in which the radicals R_(e) are chosen from, independently of each other, a hydrogen atom and a C₁-C₄ alkyl radical; a cyano radical; and a halogen atom; the radicals R₄ are chosen from, independently of each other: a linear C₁-C₄ alkyl radical; a hydroxyl radical; a C₁-C₄ alkoxy radical; a C₁-C₄ monohydroxyalkoxy or polyhydroxyalkoxy radical; an amino radical optionally substituted with one or two C₁-C₄ alkyl radicals, which may be identical or different, the one or two alkyl radicals optionally bearing at least one hydroxyl radical; the two alkyl radicals optionally forming, together with the nitrogen atom to which they are attached, a 5 or 6-membered heterocycle optionally comprising another heteroatom identical to or different from nitrogen, and optionally substituted with at least one methyl, hydroxyl, amino, monomethylamino or dimethyl amino radicals; a group R_(a)CO—NR_(a)′— wherein the radical R_(a) is chosen from a C₁-C₄ alkyl radical and the radical R_(a)′ is chosen from a hydrogen atom and a C₁-C₄ alkyl radical; a group (R_(b))₂N—CO— wherein the radicals R_(b) are chosen from, independently of each other, a hydrogen atom and a C₁-C₄ alkyl radical; a group (R_(c))₂N—CO—NR_(c)— wherein the radicals R_(c) are chosen from, independently of each other, a hydrogen atom and a C₁-C₄ alkyl radical; a group (R_(d))₂N—SO₂ in which the radicals R_(d) are chosen from, independently of each other, a hydrogen atom and a C₁-C₄ alkyl radical; a group R_(e)SO₂—NR_(e)— wherein the radicals R_(e) are chosen from, independently of each other, a hydrogen atom and a C₁-C₄ alkyl radical; a cyano radical; and a halogen atom; the radicals R₅ and R₆, which may be identical or different, are chosen from: a hydrogen atom; a linear or branched, saturated, acyclic, optionally substituted C₁-C₈ hydrocarbon-based chain, optionally interrupted with at least one heteroatom and/or with at least one group comprising at least one heteroatom, wherein the at least one heteroatom is chosen from oxygen, nitrogen, sulfur, CO, SO, and SO₂, or combinations thereof; and wherein the hydrocarbon-based chain does not comprise nitro, nitroso, peroxo, or diazo functions and being attached to the nitrogen atom via a carbon atom; a radical (R_(f)SO₂—) wherein the radical R_(f) is chosen from a C₁-C₄ alkyl radical; a benzyl radical optionally substituted with at least one hydroxyl and/or amino radicals; the radicals R₅ and R₆ optionally forming, with the nitrogen atom to which they are attached, a saturated or unsaturated, optionally substituted 5- or 7-membered heterocycle, optionally comprising another heteroatom that is identical to or different from nitrogen; one of the radicals R₅ and R₆ optionally forming, with the nitrogen atom to which it is attached and with a radical R₄ located ortho to the group NR₅R₆, an optionally substituted 5- or 6-membered heterocycle of formula (III) below

wherein: o is chosen from 0 and 1; Rx and Ry are chosen from, independently of each other, a hydrogen atom and a methyl radical; the radicals R₅ and R₆ optionally forming, with the nitrogen atom to which they are attached and each with a radical R₄ located ortho to the group NR₅R₆, an optionally substituted 5- or 6-membered heterocycle of formula (IV) below:

wherein: o is chosen from 0 and 1; Rx and Ry are chosen from, independently of each other, a hydrogen atom and a methyl radical; n is chosen from 0, 1, and 2; when n is 0 or 1, the unsubstituted carbon atom bears a hydrogen atom; n′ is chosen from 0, 1, 2, 3, and 4 when n′ is 0, 1, 2, or 3, the unsubstituted carbon atom bears a hydrogen atom; n″ is chosen from 0, 1, 2, 3, and 4 when n″ is 0, 1, 2, or 3, the unsubstituted carbon atom bears a hydrogen atom; and the electrical neutrality of the compounds of formula (I) or (II) being assured by at least one identical or different cosmetically acceptable anions An.
 53. A multi-compartment device, wherein a first compartment contains a composition for dyeing keratin fibers and a second compartment contains an oxidizing composition, and wherein the composition for dyeing keratin fibers, comprises, in a suitable dyeing medium, at least one cationic diazo direct dye comprising a 2-imidazolium unit, chosen from the compounds of formula (I) and (II) below, the mesomeric forms thereof, and the acid-addition salts thereof:

wherein: the radicals R₁, independently of each other, are chosen from: a linear or branched, saturated, acyclic, optionally substituted C₁-C₈ hydrocarbon-based chain, optionally interrupted with at least one heteroatom and/or with at least one group comprising at least one heteroatom, wherein the at least one heteroatom is chosen from oxygen, nitrogen, sulfur, CO, SO, and SO₂, or combinations thereof; and wherein the hydrocarbon-based chain when attached to the nitrogen atom of the imidazolium ring does not comprise nitro, nitroso, peroxo, or diazo functions; an optionally substituted phenyl radical; and an optionally substituted benzyl radical; the radicals R₂, independently of each other are chosen from: a linear C₁-C₄ alkyl radical, optionally substituted with an amino radical or a hydroxyl radical; an optionally substituted phenyl radical; and a halogen atom; the radicals R₃, independently of each other are chosen from: a linear C₁-C₄ alkyl radical, optionally substituted with an amino radical or a hydroxyl radical; a hydroxyl radical; a C₁-C₄ alkoxy radical; a C₁-C₄ monohydroxyalkoxy or polyhydroxyalkoxy radical; an amino radical optionally substituted with one or two C₁-C₄ alkyl radicals, which may be identical or different, optionally bearing at least one hydroxyl radical; a group R_(a)CO—NR_(a)′— in which the radical R_(a) is chosen from a C₁-C₄ alkyl radical and the radical R_(a)′ is chosen from a hydrogen atom and a C₁-C₄ alkyl radical; a group (R_(b))₂N—CO— wherein the radicals R_(b) are chosen from, independently of each other, a hydrogen atom and a C₁-C₄ alkyl radical; a group (R_(c))₂N—CO—NR_(c)— in which the radicals R_(c) are chosen from, independently of each other, a hydrogen atom and a C₁-C₄ alkyl radical; a group (R_(d))₂N—SO₂— in which the radicals R_(d) are chosen from, independently of each other, a hydrogen atom and a C₁-C₄ alkyl radical; a group R_(e)SO₂—NR_(e)— in which the radicals R_(e) are chosen from, independently of each other, a hydrogen atom and a C₁-C₄ alkyl radical; a cyano radical; and a halogen atom; the radicals R₄ are chosen from, independently of each other: a linear C₁-C₄ alkyl radical; a hydroxyl radical; a C₁-C₄ alkoxy radical; a C₁-C₄ monohydroxyalkoxy or polyhydroxyalkoxy radical; an amino radical optionally substituted with one or two C₁-C₄ alkyl radicals, which may be identical or different, the one or two alkyl radicals optionally bearing at least one hydroxyl radical; the two alkyl radicals optionally forming, together with the nitrogen atom to which they are attached, a 5 or 6-membered heterocycle optionally comprising another heteroatom identical to or different from nitrogen, and optionally substituted with at least one methyl, hydroxyl, amino, monomethylamino or dimethyl amino radicals; a group R_(a)CO—NR_(a)′— wherein the radical R_(a) is chosen from a C₁-C₄ alkyl radical and the radical R_(a)′ is chosen from a hydrogen atom and a C₁-C₄ alkyl radical; a group (R_(b))₂N—CO— wherein the radicals R_(b) are chosen from, independently of each other, a hydrogen atom and a C₁-C₄ alkyl radical; a group (R_(c))₂N—CO—NR_(c)— wherein the radicals R_(c) are chosen from, independently of each other, a hydrogen atom and a C₁-C₄ alkyl radical; a group (R_(d))₂N—SO₂ in which the radicals R_(d) are chosen from, independently of each other, a hydrogen atom and a C₁-C₄ alkyl radical; a group R_(e)SO₂—NR_(e)— wherein the radicals R_(e) are chosen from, independently of each other, a hydrogen atom and a C₁-C₄ alkyl radical; a cyano radical; and a halogen atom; the radicals R₅ and R₆, which may be identical or different, are chosen from: a hydrogen atom; a linear or branched, saturated, acyclic, optionally substituted C₁-C₈ hydrocarbon-based chain, optionally interrupted with at least one heteroatom and/or with at least one group comprising at least one heteroatom, wherein the at least one heteroatom is chosen from oxygen, nitrogen, sulfur, CO, SO, and SO₂, or combinations thereof; and wherein the hydrocarbon-based chain does not comprise nitro, nitroso, peroxo, or diazo functions and being attached to the nitrogen atom via a carbon atom; a radical (R_(f)SO₂—) wherein the radical R_(f) is chosen from a C₁-C₄ alkyl radical; a benzyl radical optionally substituted with at least one hydroxyl and/or amino radicals; the radicals R₅ and R₆ optionally forming, with the nitrogen atom to which they are attached, a saturated or unsaturated, optionally substituted 5- or 7-membered heterocycle, optionally comprising another heteroatom that is identical to or different from nitrogen; one of the radicals R₅ and R₆ optionally forming, with the nitrogen atom to which it is attached and with a radical R₄ located ortho to the group NR₅R₆, an optionally substituted 5- or 6-membered heterocycle of formula (III) below

wherein: o is chosen from 0 and 1; Rx and Ry are chosen from, independently of each other, a hydrogen atom and a methyl radical; the radicals R₅ and R₆ optionally forming, with the nitrogen atom to which they are attached and each with a radical R₄ located ortho to the group NR₅R₆, an optionally substituted 5- or 6-membered heterocycle of formula (IV) below:

wherein: o is chosen from 0 and 1; Rx and Ry are chosen from, independently of each other, a hydrogen atom and a methyl radical; n is chosen from 0, 1, and 2; when n is 0 or 1, the unsubstituted carbon atom bears a hydrogen atom; n′ is chosen from 0, 1, 2, 3, and 4 when n′ is 0, 1, 2, or 3, the unsubstituted carbon atom bears a hydrogen atom; n″ is chosen from 0, 1, 2, 3, and 4 when n″ is 0, 1, 2, or 3, the unsubstituted carbon atom bears a hydrogen atom; and the electrical neutrality of the compounds of formula (I) or (II) being assured by at least one identical or different cosmetically acceptable anions An.
 54. A composition according to claim 35, wherein a cationic diazo direct dye of formula (I) and (II) is not the compounds below:

and also the mesomeric forms thereof, the acid-addition salts thereof. 